rm builder

[ak]

Hi Bob,
I see you are on line and i have a question about doing a leakdown test on my 509 that you requested for a cam grind selection,this is adam kacan,if you dont figure out who it is by my ak forum name,anyways i got a new matco leakdown tester and was performing the test last night and the air turn the motor off of tdc,and i cant hold it,so i was wondering about removing all the rockers so all the valves stay closed and do it that way,but does it matter where the piston is postioned in the cylinder?i would like to get this done today if possible.
Also if you dont remember the engine is on a cradle out of the boat already and easy access to everything,so i cant do the test warm.

[mrhorsepower1]

Your best position to have the piston in is about 2-5 degrees before TDC actually. The pistons and rings will be the squarest in the cylinder at this point. If you can have a second set of hands to perform the test is ideal. One person can hold the engine from "backing" up with a breaker bar, while the other operates the leak down tester. If the engine has sat for along period of time , doing a warm test is ideal. If you get some leakage out the valves it may be do to carbon between the valve and set. You can take a plastic dead blow hammer and lightly tap on the center of the valve with the rocker off and the air hooked up. This will sometimes clear the carbon or rust for a more accurate test since you can not run the engine.

Best Regards,

Dean Gellner